In situ study of hydride precipitation kinetics and re-orientation in Zircaloy using synchrotron radiation

The orientation and distribution of hydrides formed in zirconium alloy nuclear fuel cladding can strongly influence material behavior and in particular resistance to crack growth. The hydride microstructure and hydride platelet orientation (whether in-plane or radial relative to the cladding tubes) are crucial to determining cladding failure limits during mechanical testing. Hydride formation is normally studied by post-facto metallography, performed at room temperature and in the absence of applied stress. This study uses synchrotron radiation to observe in situ the kinetics of hydride dissolution and precipitation in previously hydrided Zircaloy samples. The experiments allow the direct observation of hydride dissolution, re-precipitation, and re-orientation, during heating and cooling under load. The solubility limits and the hydride-matrix orientation relationship determined from in situ experiments were in good agreement with previous post-facto examinations of bulk materials. The present measurements performed under stress and at temperature showed a characteristic diffraction signature of reoriented hydrides. The results suggest a threshold stress for hydride re-orientation between 75 and 80 MPa for the microstructure/texture studied. These results are discussed in light of existing knowledge.     

Mapping geological stages of climate-dependent iron and clay weathering alteration on lithologically uniform sedimentary units using Thematic Mapper imagery (Tertiary Duero Basin,Spain)

Weathering processes are responsible for slight surface mineralogical differences allowing the distinction between lithologically similar geological units using Thematic Mapper (TM) data. Two different stages throughout time of overlying iron alteration are notoriously distinctive on the imagery and laboratory spectra. Their diverse spectral behaviour follows the dominant iron hydroxide with kaolinite and carbonate crusts on the Pliocene Ochre Alteration typical of a humid warm climate, compared with the dominant nonhydratated iron oxides with smectite on the Miocene Red Alteration developed under a mediterranean dry climate. Iron materials with carbonate hinder appearance of the typical iron absorption features in the visible wavebands. Therefore, the iron weathering alteration coatings will be obscured on the imagery when it is developed on carbonate sediments or detritic sediments with carbonate cement or matrix. The presence of carbonate within the sediment as cement or alteration product decreases the overall reflectance of laboratory nonconsolidated rocks and the clay size fraction from rocks, apart from smoothing the 2200 nm absorption typical of OH-bearing minerals. The presence of carbonate cement and carbonate crusts favours the differentiation of some units. Digital mapping through image processing of different series of digital data leads to a sequential masking of classes to produce a final map. The sequence of masking produces different maps which can be used as a tool to model aspects of the sedimentary basin and geological processes throughout time.     

Toward a computational model of aspect and verb semantics

The authors examine aspect and the semantic classification of verbs, two areas of concern for natural language processing not often studied in the context of computational linguistics. A five-way aspectual classification system is defined on the basis of three aspectual features, making use of the concept of predicates as event structures. The aspectual value of a sentence can differ from that of its predicate due to the operation of aspectual functions. Sentential aspect is ultimately derived from the operation of various components of the sentence on the aspectual properties of the predicate. A system of twelve semantic features describing the core meaning of verbs provides a level of specificity that can distinguish different senses of verbs and could be used to predict their consequent syntactic and semantic behavior. The computational utility of these models will be tested on a working machine translation system.Also affiliated with Siemens Public Switching SystemsThis paper is written in conjunction with a research project funded by the Texas Higher Education Coordinating Board Advanced Research Programs, Grant No. 1631. The paper is a collective effort of the five authors. Although individual members of the group wrote particular portions, the entire group discussed and revised all parts of this work. We are jointly responsible for its contents. We wish to thank the journal's anonymous referees for their extremely helpful comments.     

Vector control methods for induction machines: an overview

In the last three decades, different vector control methods (field-oriented control (FOC), field acceleration method (FAM), universal field orientation (UFO), direct self control (DSC) and Takahashi method among others) have been proposed. It is difficult for students and nonspecialists to understand the drawbacks and advantages of each one. With this in mind, the objective of this paper is to propose a clear classification and comparison of them     

Interplay of advances between theory, research, and application in treatment interventions aimed at behavior problem children and adolescents.

This article examines the important role that the interplay between theory, research, and application has in fostering breakthroughs in the treatment of clinical problems. This issue is presented in the context of an ongoing program of psychotherapy research that targets for intervention of Hispanic behavior problem youth and their families. Findings and breakthroughs in structural family therapy, the measurement of family and child psychodynamic functioning, the development of culturally appropriate interventions, the role of attrition as a measure of outcome, and the investigation of theoretically postulated mechanisms in behavior change are discussed. Recommendations for future research directions are made. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Coagulating and lipolytic activities of artisanal lamb rennet pastes

Lamb rennet pastes were prepared by the procedure most commonly used by Idiazabal cheese manufacturers. We studied the effects on their coagulating and lipolytic activities of the state of the stomach at the time of death (full of milk or empty), the amount of NaCl added, the origin of the lambs and paste storage time. Coagulating activities were generally between 155 and 363 units/g tissue. Pastes prepared from stomachs of lambs from slaughterhouse flocks had significantly higher coagulating activities than those of lambs from separate flocks. No significant decrease in coagulating activity was observed after 1 year storage at 4 degrees C. Chymosin represented 75-80% of the total coagulating activity with the remainder being pepsin. Rennet paste extracts with pH < 4.7 did not have increased coagulating activities when their pH was lowered to 2.0, while those with pH > 5.2 had activities 1.5-fold those before treatment. Lipase activity was higher in extracts of rennet pastes prepared using the stomachs of lambs that arrived at the slaughterhouse in the morning just prior to slaughter than in those prepared with the stomachs of lambs that had arrived on the previous evening. However, the reverse was the case for esterase activity. Activating the coagulating activity by pH cycling completely destroyed both lipolytic activities. Storage at 4 degrees C for > 1 year did not affect esterase activity but lipase activity decreased substantially after 4-5 months. Lipase, but not esterase, activity was responsible for the liberation of short-chain free fatty acids from ovine milk fat.